29/07/2026
Lukewarm water is one of the most common calls we get from flats on communal heating, and it is almost never the tap.
This one came in as hot water that never quite got hot. Inside the heat interface unit we found a faulty temperature sensor and a blending valve that had failed, plus blockages restricting the flow through the unit.
We replaced both parts, cleared the blockages, and had the hot water back to a steady 55ยฐC before we left.
If your building runs on a communal or district heating system, the HIU in your cupboard does the job a boiler would do in a normal home. When a sensor or a valve inside it drifts, you get lukewarm water, weak flow, or heating that will not hold temperature. In most cases it is a repair, not a replacement.
We service and repair HIUs across London for residents, landlords and managing agents.
๐ 020 3764 2713
๐ https://ph247.co.uk/heat-interface-unit-service/